Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Bacillus thuringiensis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMed2003

Antibacterial activity of Cry- and Cyt-proteins from Bacillus thuringiensis ssp. israelensis.

Mosquitocidal endotoxins Cry4B, Cry11A, and CytA from Bacillus thuringiensis ssp. israelensis as well as the products of their limited proteolysis display antibacterial activity relative to Micrococcus luteus. The endotoxin Cry11A also induces the lysis of the micrococcus protoplasts. Potassium and sodium ions and N-acetylgalactosamine increased the antibacterial effect of Cry11A, whereas glucose and N-acetylglucosamine inhibited it. The endotoxin Cry11A displays the antibacterial effect on some other microorganisms.

Bacillus thuringiensis↗
PubMed1968

Biochemical homology between crystal and spore protein of Bacillus thuringiensis.

The crystalline inclusion of Bacillus thuringiensis, dissolved in 8 m urea containing 10% 2-mercaptoethanol and dialyzed to pH 8.3 to 8.5, was compared with a fraction obtained by the same extraction procedure from spores broken by dry rupture. The two fractions behaved similarly on chromatography with Sephadex G-100 and diethylaminoethyl cellulose. The preparations behaved identically on acrylamide gel electrophoresis at pH 12 and pH 9.5. Further, peptide maps of the two fractions obtained after digestion with trypsin were almost superimposable. Amino acid analyses of the crystal and spore fraction were closely similar; discrepancies are attributed to contamination of the spore extract with small amounts of other proteins. It is concluded that a significant portion of the spore protein is identical with the crystal protein.

Amino Acids↗
PubMed1992

Molecular characterization of two novel crystal protein genes from Bacillus thuringiensis subsp. thompsoni.

Two genes encoding the predominant polypeptides of Bacillus thuringiensis subsp. thompsoni cuboidal crystals were cloned in Escherichia coli and sequenced. The polypeptides have electrophoretic mobilities of 40 and 34 kDa, with the deduced amino acid sequences predicting molecular masses of 35,384 and 37,505 Da, respectively. No statistically significant similarities were detected between the 40- or 34-kDa crystal protein and any other characterized B. thuringiensis crystal protein, nor were they detected between the 40- and 34-kDa crystal proteins. A 100-MDa plasmid carries both crystal protein genes, which appear to be part of an operon, with the 40-kDa gene 64 nucleotides upstream of the 34-kDa gene. Both crystal proteins are synthesized in approximately the same amounts. Even though small compared with other crystal proteins, the 34-kDa crystal protein has insecticidal activity against lepidopteran larvae (Manduca sexta). The 40-kDa polypeptide appears to have no insecticidal activity, but it could have a role in crystal structure.

Amino Acid Sequence↗
PubMed1987

Cloning and heterologous expression of an insecticidal delta-endotoxin gene from Bacillus thuringiensis var. aizawai IC1 toxic to both lepidoptera and diptera.

Bacillus thuringiensis var. aizawai IC1 synthesises an insecticidal protein delta-endotoxin (130-135 kDa) that is toxic to both lepidopteran and dipteran larvae, and cross-reacts immunologically with certain monospecific lepidopteran toxins. A 166-kb plasmid from this bacterium was found to hybridise with an intragenic probe derived from the clone B. thuringiensis var. sotto lepidopteran-specific delta-endotoxin gene. A strongly hybridising 5.2-kb SstI fragment from var. aizawai plasmid DNA was cloned in pUC18. After subcloning of this DNA in Escherichia coli, recombinants were obtained that synthesised large amounts of a 130-135-kDa protein. The protein was deposited in the cytoplasm as microscopically visible inclusion bodies and lysates of these cells were found to be toxic to both lepidopteran and dipteran larvae by comparison with controls. The structural basis for the dual specificity of this var. aizawai toxin is now amenable to further study.

Bacillus thuringiensis↗
PubMed2003

Cloning and characterization of a cytolytic and mosquito larvicidal delta-endotoxin from Bacillus thuringiensis subsp. darmstadiensis.

The cytolytic delta-endotoxin gene from Bacillus thuringiensis subsp. darmstadiensis was amplified from genomic DNA by PCR by using primers designed from the sequence of cyt2Aa1 gene of B. thuringiensis subsp. kyushuensis. DNA sequence analysis revealed an open reading frame translating to a 259-amino acid sequence. The cloned gene was designated cyt2Aa2. This gene was highly expressed in Escherichia coli as inclusion bodies that could be solubilized in 50 m M Na(2)CO(3), pH 10.5. Activation of the solubilized protoxin by proteinase K (1% wt/wt, proteinase K/protoxin) yielded the active fragment of about 23 kDa. Cyt2Aa2 showed high hemolytic activity against sheep erythrocytes (hemolytic end- point 0.25 microgram/ml) and was toxic to Culex quinquefasciatus and Aedes aegypti larvae (LC(50) 0.5-1.0 microgram/ml).

Aedes↗
PubMed2001

How Bacillus thuringiensis has evolved specific toxins to colonize the insect world.

Bacillus thuringiensis is a bacterium of great agronomic and scientific interest. Together the subspecies of this bacterium colonize and kill a large variety of host insects and even nematodes, but each strain does so with a high degree of specificity. This is mainly determined by the arsenal of crystal proteins that the bacterium produces during sporulation. Here we describe the properties of these toxin proteins and the current knowledge of the basis for their specificity. Assessment of phylogenetic relationships of the three domains of the active toxin and experimental results indicate how sequence divergence in combination with domain swapping by homologous recombination might have caused this extensive range of specificities.

Animals↗
PubMedDate not supplied

PCR-based identification of Bacillus thuringiensis isolated from soil samples in Nigeria.

Six isolates of Bacillus thuringiensis isolated from soil samples confirmed to be toxic to mosquito larvae were differentiated using a PCR-Based technique. Three of these isolates initially identified using a serological technique were further differentiated with the PCR amplification of the delta-endotoxin target sequences. Using the total DNA of isolates as template, at least four isolates yielded amplicons one or all the crystal protein genes, cryI a, b, c, or II with sizes ranging from 238-1070 bp. None of these isolates yielded an amplicon for any of Cry IV A, B and D tested. Of the four isolates identified by PCR technique one isolate remained unidentified by serology.

Animals↗
PubMed2006

Co-expression of the mosquitocidal toxins Cyt1Aa and Cry11Aa from Bacillus thuringiensis subsp. israelensis in Asticcacaulis excentricus.

The cyt1Aa gene from Bacillus thuringiensis subsp. israelensis (Bti), whose product synergizes other mosquitocidal toxins, and functions as a repressor of resistance developed by mosquitoes against Bacilli insecticides, was introduced into the aquatic Gram-negative bacterium Asticcacaulis excentricus alongside the cry11Aa gene. The genes were introduced as an operon, but although mRNA was detected for both genes, no Cyt1Aa toxin was detected. Both proteins were expressed using a construct in which a promoter was inserted upstream of each gene. Recombinant A. excentricus expressing both toxins was found to be approximately twice as toxic to third instar larvae of Culex quinquefasciatus as transformants expressing just Cry11Aa.

Animals↗
PubMed1993

A rapid and sensitive in vitro assay for the activity of Bacillus thuringiensis delta-endotoxins.

1. Activated delta-endotoxins from Bacillus thuringiensis strains toxic to lepidopteran larvae inhibit K(+)-dependent accumulation of amino acids into brush border membrane vesicles (BBMV) from the midgut of the susceptible species Bombyx mori. 2. The activated toxins interfere with the K(+)-dependent uptake of histidine into BBMV only if they are effectively active in vivo. 3. To calculate IC50 values (the toxin concentration which determines 50% of the effect), dose-response curves were performed for each toxin. The values obtained correlate well with the LD50 determined by bioassay. 4. This amino acid inhibition test could represent a rapid (3-6 hr, compared to 3-4 days for bioassay) and sensitive method for the screening of larvicidal activity of known or new recombinant delta-endotoxins.

Animals↗
PubMed2001

Cross-resistance and stability of resistance to Bacillus thuringiensis toxin Cry1C in diamondback moth.

We tested toxins of Bacillus thuringiensis against larvae from susceptible, Cry1C-resistant, and Cry1A-resistant strains of diamondback moth (Plutella xylostella). The Cry1C-resistant strain, which was derived from a field population that had evolved resistance to B. thuringiensis subsp. kurstaki and B. thuringiensis subsp. aizawai, was selected repeatedly with Cry1C in the laboratory. The Cry1C-resistant strain had strong cross-resistance to Cry1Ab, Cry1Ac, and Cry1F, low to moderate cross-resistance to Cry1Aa and Cry9Ca, and no cross-resistance to Cry1Bb, Cry1Ja, and Cry2A. Resistance to Cry1C declined when selection was relaxed. Together with previously reported data, the new data on the cross-resistance of a Cry1C-resistant strain reported here suggest that resistance to Cry1A and Cry1C toxins confers little or no cross-resistance to Cry1Bb, Cry2Aa, or Cry9Ca. Therefore, these toxins might be useful in rotations or combinations with Cry1A and Cry1C toxins. Cry9Ca was much more potent than Cry1Bb or Cry2Aa and thus might be especially useful against diamondback moth.

Animals↗
PubMed1999

Two novel delta-endotoxin gene families cry26 and cry28 from Bacillus thuringiensis ssp. finitimus.

Genes cry26Aal and cry28Aal were cloned from Bacillus thuringiensis ssp. finitimus strain B-1166 VKPM. This strain forms insecticidal crystal bodies either outside or inside the exosporium. The deduced amino acid sequence of the cry26Aal gene product included seven residues determined to be an N-terminal part of a chymotrypsin-treated delta-endotoxin isolated from the same strain. Earlier this protein was detected in both free and spore-associated types of crystals [Revina et al., Biokhimia (1999) in press]. Neither BtI nor BtII promoter sequences were found upstream of the open reading frames in both genes. Southern hybridization has shown that the surroundings of both genes at least 3 kb upstream and downstream of the open reading frames are unique. We suggest that the protein Cry26Aal in both types of crystal bodies is synthesized under the control of one and the same genomic locus.

Amino Acid Sequence↗
PubMed2006

Development of a recombinant strain of Bacillus thuringiensis subsp. kurstaki HD-73 that produces the endochitinase ChiA74.

Bacillus thuringiensis subsp. kurstaki HD-73 was transformed with the homologous endochitinase gene chiA74 of B. thuringiensis subsp. kenyae LBIT-82 under the regulation of its own promoter and Shine-Dalgarno sequence. The plasmid, pEHchiA74, which harbors chiA74, was detected by southern blot analysis and showed high segregational stability when the recombinant strain was grown in a medium without antibiotic. The recombinant bacterium transformed with pEHchiA74 showed an improvement in chitinolytic activity three times that of the wild-type strain. Expression of ChiA74 did not have any deleterious effect on the crystal morphology and size, but sporulation and Cry1Ac production in rich medium (nutrient broth with glucose) was reduced by approximately 30%. No significant increase in the toxicity of the transformant bacterium toward Plutella xylostella was detected using the same amount of total protein. However, it is possible that ChiA74 synthesis compensated for the decrease in net Cry1Ac synthesis and toxicity observed with the recombinant strain.

Animals↗
PubMed1988

Comparative toxicity of Bacillus thuringiensis var. israelensis crystal proteins in vivo and in vitro.

Bacillus thuringiensis var. israelensis crystal proteins were purified by FPLC on a Mono Q column to yield 130, 65, 28, 53, 30-35 and 25 kDa proteins. All the purified proteins killed Aedes aegypti larvae after citrate precipitation, but the 65 kDa protein was the most toxic. A precipitated mixture of 27 and 130 kDa proteins was almost as toxic as solubilized crystals. In assays against a range of insect cell lines, the activated form (25 kDa) of the 27 kDa protein was generally cytotoxic with the lowest LC50 values in vitro. By contrast, the activated forms of the 130 kDa and 65 kDa protoxins (53 kDa and 30-35 kDa proteins, respectively) were much more specific than the 25 kDa protein in their action on dipteran cells, and each showed a unique toxicity profile which, in the case of the 130 kDa preparation, was restricted to Anopheles and Culex cell lines.

Aedes↗
PubMed1985

Molecular cloning and the nucleotide sequence of the Mr 28 000 crystal protein gene of Bacillus thuringiensis subsp. israelensis.

The Mr 28.000 crystal protein gene of Bacillus thuringiensis subspecies israelensis has been cloned into pBR322 as part of a 9.7 kb HindIII fragment. From hybridization experiments of recombinant p425 DNA with B.t. subspecies israelensis RNA from different stages of growth it was concluded that transcription of the gene is restricted to early sporulation stages. Nucleotide sequence analysis revealed the presence of a large open reading frame with a coding capacity of 249 amino acids (Mr 27.340). Nuclease S1 mapping demonstrated that transcription starts 44 nucleotides upstream of the initiation codon. A Shine-Dalgarno sequence (AAGGAG) was found 10 nucleotides upstream of the translation startpoint. At the 3'-end of the gene a complex secondary structure was found immediately after the stop-codon. Despite the presence of these regulation signals only limited expression in E. coli was detected. This can be explained by assuming that B.t. subsp. israelensis promotor sequences are poorly recognized by E. coli RNA polymerase.

Amino Acid Sequence↗
PubMed2001

The alpha-helix 4 residue, Asn135, is involved in the oligomerization of Cry1Ac1 and Cry1Ab5 Bacillus thuringiensis toxins.

The insecticidal Cry toxins produced by the bacterium Bacillus thuringiensis are comprised of three structural domains. Domain I, a seven-helix bundle, is thought to penetrate the insect epithelial cell plasma membrane through a hairpin composed of alpha-helices 4 and 5, followed by the oligomerization of four hairpin monomers. The alpha-helix 4 has been proposed to line the lumen of the pore, whereas some residues in alpha-helix 5 have been shown to be responsible for oligomerization. Mutation of the Cry1Ac1 alpha-helix 4 amino acid Asn135 to Gln resulted in the loss of toxicity to Manduca sexta, yet binding was still observed. In this study, the equivalent mutation was made in the Cry1Ab5 toxin, and the properties of both wild-type and mutant toxin counterparts were analyzed. Both mutants appeared to bind to M. sexta membrane vesicles, but they were not able to form pores. The ability of both N135Q mutants to oligomerize was also disrupted, providing the first evidence that a residue in alpha-helix 4 can contribute to toxin oligomerization.

Animals↗
PubMed1991

In vivo generation of hybrids between two Bacillus thuringiensis insect-toxin-encoding genes.

The parasporal crystal of Bacillus thuringiensis is composed of polypeptides highly toxic to a number of insect larvae. The structural genes (cryIA) encoding the Lepidoptera-specific toxin from different bacterial strains diverge primarily in a single hypervariable region, whereas the N-terminal and C-terminal parts of the proteins are highly conserved. In this report, we describe the generation of hybrid genes between two cryIA genes. Two truncated cryIA genes were cloned in a plasmid vector in such way as to have only the hypervariable region in common. The two truncated cryIA genes were separated by the tetracycline-resistance determinant (or part of it). In vivo recombination between the hypervariable regions of the cryIA genes reconstituted an entire hybrid cryIA gene. Direct sequence analysis of 17 recombinant plasmids identified eleven different crossover regions which did not alter the reading frame and allowed the production of eight different hybrid proteins. The recombination events were independent from the RecA function of Escherichia coli. Some of the hybrid gene products were more specific in their insecticidal action and one had acquired a new biological activity.

Amino Acid Sequence↗
PubMed1992

Insecticidal activity and processing in larval gut juices of genetically engineered 130-kDa proteins of Bacillus thuringiensis subsp. aizawai.

The 130-kDa insecticidal protein (IP) of Bacillus thuringiensis subsp. aizawai is proteolytically processed in the gut juice of susceptible insect larvae to yield an insecticidally active 60-kDa fragment. Twenty-seven mutant IP genes with the replacement of codons for Arg and Lys with codons for Gln in the active fragment and its adjacent regions of the 130-kDa IP were constructed by site-directed mutagenesis and expressed in Escherichia coli cells. The produced mutant IPs at Arg87, Arg131, Arg198, Arg311, Arg368, Arg402, Arg458, Arg502, Arg512, Arg524, Arg526, Arg528, and Arg601 had reduced insecticidal activity against Spodoptera litura larvae. The mutant at Arg601 was sensitive to proteolytic digestion in the gut juice of S. litura larvae. Although the mutants at Arg619, Lys622, and Lys637 had nearly the same activity as that of the wild type, the mutant with the triple replacement at Arg619, Lys622, and Lys637 was 2.5 times more active against S. litura larvae than the wild type. This triple mutant showed a slightly different processing profile in the gut juice than that of the wild type.

Amino Acid Sequence↗
PubMed2000

Genome stability of Bacillus thuringiensis subsp. israelensis isolates.

Swedish soil isolates biochemically classified as Bacillus thuringiensis subsp. israelensis were further examined for genetic diversity by multilocus enzyme electrophoresis (MLEE), random amplified polymorphic DNA analysis (RAPD), pulse field gel electrophoresis (PFGE), and Southern blotting, and were compared with reference strains. All the tested strains belonging to the Bt. israelensis serotype H14 were found to be identical, as judged from the RAPD analysis. MLEE analysis gave a similar result; only one H14 strain was found to differ from the remaining H14 strains by one null allele. PFGE analysis confirmed a very close relationship between the H14 strains but revealed an SfiI restriction fragment of variable size. Southern blot analyses were carried out with probes for the chromosomally encoded flagellin gene(s) and the plasmid-encoded mosquitocidal toxins. All probes gave similar hybridization patterns in the H14 strains. The mosquito toxin probes hybridized only to the H14 strains, except for one probe hybridizing to strain 6:3, which was originally isolated from the same soil sample as strains 6:11 and 6:12. Because the RAPD, MLEE, and PFGE analyses showed that strain 6:3 appears to be unrelated to strains 6:11 and 6:12, the presence of a mosquito toxin sequence in strain 6:3 may suggest that gene transfer has occurred.

Animals↗